﻿/*
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at 
 * 
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 *  
 */

namespace biz.ritter.javapi.util
{
    /**
     * An {@code Iterator} is used to sequence over a collection of objects.
     * Conceptually, an iterator is always positioned between two elements of a
     * collection. A fresh iterator is always positioned in front of the first
     * element.
     * 
     * If a collection has been changed since its creation, methods {@code next} and
     * {@code hasNext()} may throw a {@code ConcurrentModificationException}.
     * Iterators with this behavior are called fail-fast iterators.
     * 
     * @param <E>
     *            the type of object returned by the iterator.
     */
    public interface Iterator<E> {
        /**
         * Returns whether there are more elements to iterate, i.e. whether the
         * iterator is positioned in front of an element.
         * 
         * @return {@code true} if there are more elements, {@code false} otherwise.
         * @see #next
         */
        bool hasNext();

        /**
         * Returns the next object in the iteration, i.e. returns the element in
         * front of the iterator and advances the iterator by one position.
         * 
         * @return the next object.
         * @throws NoSuchElementException
         *             if there are no more elements.
         * @see #hasNext
         */
        E next();

        /**
         * Removes the last object returned by {@code next} from the collection.
         * This method can only be called once after {@code next} was called.
         * 
         * @throws UnsupportedOperationException
         *             if removing is not supported by the collection being
         *             iterated.
         * @throws IllegalStateException
         *             if {@code next} has not been called, or {@code remove} has
         *             already been called after the last call to {@code next}.
         */
        void remove();
    }
}
